1302.1 The water system serving the District consists of two primary components: the water supply and treatment system, and the water distribution system.

1302.2 DC Water was created by District law in 1996, with the approval of the United States Congress, as an independent authority of District government with a separate legal existence. As of 2016, DC Water distributes safe, treated drinking water to all residents, workers, and visitors in the District.

1302.3 Since 2006, there has been an evolution in the way water management is approached: while previously siloed as separate systems, potable water, wastewater, and stormwater are now managed together. This approach focuses on optimal outcomes, with all components considered together during the planning process. The whole water cycle, from capture, treatment, and reuse, is now integrated at both the local and District-wide scale. Thus, some of the policies and actions below may apply to drinking water infrastructure, as well as to wastewater and stormwater systems.

1302.4 The water supply and treatment system includes raw water sources, pipelines carrying this water to treatment plants, and the water treatment plants themselves. USACE operates and maintains these facilities and supplies treated water to several distributors. These distributors (which include DC Water) deliver water to over one million users in Washington, DC and Northern Virginia.

1302.5 The Washington Aqueduct water system was commissioned by Congress and built by USACE in the 1850s to provide the nation's capital with a plentiful water source. It has been in continuous operation ever since and is the only public water supply in the United States where the federal government has a direct role in providing drinking water.

1302.6 The Washington Aqueduct system is composed of the Great Falls and Little Falls intakes on the Potomac River, the Dalecarlia and McMillan Reservoirs, the Georgetown Conduit and Reservoir, the Washington City Tunnel, and the East Shaft Pump Station. The sand filtration site located at the McMillan Reservoir and Water Treatment Plan was decommissioned in 1986 and is no longer part of the water treatment system. Figure 13.1 shows the Washington Aqueduct system.

1302.7 Figure 13.1: Washington Aqueduct System

(Source: Washington Aqueduct, 2018)

1302.8

The Potomac River is the source of all water treated and delivered to customers by the Washington Aqueduct, a federally owned and operated water supply agency. To ensure that this supply meets the needs of the Washington Aqueduct's customers, the Low Flow Allocation Agreement (LFAA) was created in 1978. The agreement was signed by the federal government, Maryland, Virginia, and the District of Columbia. In addition to the Washington Aqueduct, the Washington Suburban Sanitary Commission and the Fairfax County Water Authority are the affected water providers. The agreement, through a formula for allocating Potomac River water, ensures that the downstream user, the Washington Aqueduct, has an appropriate allocation of available water. With the construction of the Jennings Randolph and Little Seneca reservoirs, the additional water available to be released has been sufficient to operate through major droughts in 1999 and 2002. While the provisions of the LFAA have not been triggered, every year its parties conduct a drought exercise to review the procedures that would be used in a more significant drought emergency.

1302.9 In 1982, the major water utilities and the Interstate Commission on the Potomac River Basin (ICPRB) signed the Water Supply Coordination Agreement (WSCA), which required the major water suppliers to coordinate their operations during drought emergencies. The agreement also required that a 20-year study of supply and demand be prepared and updated every five years. Furthermore, it included cost-sharing agreements for new facilities and subsequently included the Jennings Randolph and Little Seneca reservoirs that serve as a backup water supply during droughts.

1302.10 The most recent ICPRB study, called the 2015 Washington Metropolitan Area Water Supply Study, estimated annual demand to be 529 million gallons per day (mgd), a 12 percent increase from the 486 mgd previously estimated for 2015. The study also forecasted a growth in annual demand to 545 mgd in 2040. Although the study found that the system can meet the projected demand under normal conditions, severe drought conditions could trigger emergency water use, which would stress system reservoir volumes.

1302.11 The historic maximum production of drinking water by the Washington Aqueduct occurred in 1974 and was 284 mgd. After 1974, water demand decreased due to both declining population and increasing water conservation; however, while the District's population has been growing since 2000, water consumption has remained stable due to conservation measures. Water demand is now relatively stable. In 2017, the average daily production from the Washington Aqueduct was approximately 131 mgd, with a maximum day use of approximately 176 mgd.

1302.12 The Washington Aqueduct treats water from the Potomac River at the Dalecarlia and McMillan water treatment plants (WTPs). Both of these plants were designed for much larger populations and higher water use projections than have been realized. As a result, their treatment capacity exceeds present-day demands and peak requirements of customers. The Dalecarlia facility has a design capacity of 164 mgd and a maximum capacity of 264 mgd. The McMillan facility has a design capacity of 120 mgd and a maximum capacity of 180 mgd. DC Water's projected average water demand based on population in 2020 is 156.5 mgd. Both Dalecarlia and McMillan serve not only the needs of the District, but they also provide water to Arlington County and a portion of the Fairfax Water service area in Virginia. The total demand of all three water providers is easily met within the current operational capability of the Washington Aqueduct water treatment system.

1302.13 Potable water storage and pumping responsibilities are shared by DC Water and the Washington Aqueduct. DC Water operates four treated water pumping stations (Anacostia, Bryant Street, Fort Reno, and 16th and Alaska NW) and eight reservoirs and elevated tanks. The Washington Aqueduct operates the Dalecarlia Pump Station and three reservoirs: Foxhall, Van Ness, and Fort Reno.

1302.14 DC Water is the primary agency responsible for the District's treated water distribution system, which consists of pipes, elevated water storage tanks, valves, and public hydrants that deliver water to customers and meet other municipal needs such as fire suppression. The system is divided into nine water distribution zones (also known as service areas) based on differences in ground elevation. These areas are shown on Map 13.2.

1302.15 DC Water pumps an average of 95 mgd through the distribution system, which includes almost 1,350 miles of water mains ranging in size from four to 78 inches in diameter. This system also includes more than 36,000 valves and approximately 9,000 hydrants. The median age of the water mains is 79 years old, and some have been in service for more than a century. DC Water continually assesses the reliability and integrity of the water and sewer system pipes. To the extent that maintenance, corrosion, and break reports reveal problems, specific upgrades are factored into DC Water's 10-year Capital Improvement Program.

1302.16 Map 13.2: DC Water Service Distribution Zones

(Source: DC Water 2018)

SOURCE: District of Columbia Comprehensive Plan Act of 1984, effective April 10, 1984 (D.C. Law 5-76; 31 DCR 1049 (March 9, 1984)); as amended by District of Columbia Comprehensive Plan Act of 1984 Land Use Element Amendment Act of 1984, effective March 16, 1985 (D.C. Law 5-187; 32 DCR 873 (February 15, 1985)); as amended by District of Columbia Comprehensive Plan Amendments Act of 1989, effective May 23, 1990 (D.C. Law 8-129; 37 DCR 55 (January 5, 1990)); as amended by District of Columbia Comprehensive Plan Amendments Act of 1989 NCPC-Recommended Amendments, and Closing of Public Alleys in Square 669, S.O. 88-452, Act of 1990, effective May 23, 1990 (D.C. Law 8-132; 37 DCR 2213 (April 6, 1990)); as amended by District Government Land Use Temporary Amendment Act of 1994, effective October 1, 1994 (D.C. Law 10-190; 41 DCR 5360 (August 12, 1994)); as amended by Comprehensive Plan Amendments Act of 1994, effective October 6, 1994 (D.C. Law 10-193; 41 DCR 5536 (August 19, 1994)); as amended by District of Columbia Comprehensive Plan Act of 1984 Land Use Amendment Act of 1994, effective March 21, 1995 (D.C. Law 10-235; 42 DCR 30 (January 6, 1995)); as amended by Technical Amendments Act of 1996, effective April 18, 1996 (D.C. Law 11-110; 43 DCR 530 (February 9, 1996)); as amended by Second Technical Amendments Act of 1996, effective April 9, 1997 (D.C. Law 11-255; 44 DCR 1271 (March 7, 1997)); as amended by Comprehensive Plan Amendment Act of 1998, effective April 27, 1999 (D.C. Law 12-275; 46 DCR 1441 (February 19, 1999)); as amended by Technical Amendments Act of 1999, effective April 12, 2000 (D.C. Law 13-91; 47 DCR 520 (January 28, 2000)); as amended by Comprehensive Plan Amendment Act of 2006, effective March 8, 2007 (D.C. Law 16-300; 54 DCR 924 (February 2, 2007)); as amended by Technical Amendments Act of 2008, effective March 25, 2009 (D.C. Law 17-353; 56 DCR 1117 (February 6, 2009)); as amended by Comprehensive Plan Amendment Act of 2010, effective April 8, 2011 (D.C. Law 18-361; 58 DCR 908 (February 4, 2011)); as amended by Comprehensive Plan Amendment Act of 2021, effective August 21, 2021 (D.C. Law 24-20; 68 DCR 006918 (July 16, 2021)).